Vacuum cleaner



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Patented `[une l0, 1941 VACUUM CLEANER Ernst Fredrik Georg Fredlund, Stockholm, Sweden, assignor to Electrolux Corporation, Dover, Del., a corporation of Delaware Application March 25, 1939, Serial No. 264,063

. In Germany March Z9, 1938 2 Claims.

My invention relates to vacuum cleaners and more particularly to means for reducing noise produced by the operation ofthe vacuum cleaner.

In order to do this I make use of the principles employed in a Helmholt resonator. In accordance with my invention the vacuum cleaner is constructed with one or more spaces which are entirely closed except for a passage connecting them with the channel through which the air propelled by the fan of the vacuum cleaner is flowing. Such space or spaces and the passages are so dimensioned with respect to each other and to said channel that the natural resonant frequency of the space falls within the range f the dominant frequencies of the air which ows through the channel, that is, the frequencies which have the greatest intensity. If this is done, it has been determined that the effect is to dampen the sound Waves present in the air flowing through the channel and thus the noise transmitted by the air is greatly reduced.

Among the objects of my invention, is to provide means for accomplishing the above result, which means may be incorporated in a vacuum cleaner without increasing the size thereof. Another object is to provide such an arrangement which at the same time does not increase the resistance ofl flow of air through the cleaner.

Further objects and advantages of my invention considered in connection with the accompanying drawing, which forms part of this specication and shows a cross-sectional view of a preferred embodiment of my invention.

Referring to the drawing, reference character I0 designates the outer casing of a vacuum cleaner. Removably secured to' one end of the casing I0 is a cover member II which, when in place, clamps a dust bag ring I2 between itself and the end of the casing. Ring I2 carries a dust bag I3 which is pervious with respect to air but imperverious with respect to dust. Cover II is formed with an opening I4 to which may -be secured a hose or the like leading to a cleaning nozzle.

Mounted within casing I0 to the right of the dust bag as viewed in the ligure, is a transverse partition I5, the more central part of which is formed with perforations I6. Partition I5 serves as a support for one end of a motor-fan unit which consists of a motor I'I mounted in a hollow cylindrical structure designated generally by reference character I8. .A ring I9 of rubber or other resilient material engages one end of structure I8 and a groove formed in partition I5 to support the structure. That portion of partition I5 radially beyond the ring I9 is imperforate. Structure I8 includes a cup shaped member formed with an intake 2| for the fan. This member telescopes with a similar member 22 formed with an intake 23 for the second stage of the fan.' Member 22 in turn telescopes over a cylindrical member 24. The members 20, 22 and 24 are secured together in air-tight relationship. Fixed within the member 24 is a motor suspension ring 25 which is rigidly secured to a motor suspension wall 25 by means of tie bolts 2l. The motor Il is resiliently supported from ring 25 and wall 26 by means of coil springs 28. Wall 2B is supported Within the casing I0 by means of a resilient ring 29 carried by a rigid ring 30.

A cylindrical member 3l is supported by wall 26 and is axially in alignment with cylindrical member 24 but is spaced therefrom so as to form an annular gap 32. The outer casing I0, partition I5, cylindrical structure I8 and ring 39 thus form a space 4I which is entirely closed except for the gap 32, which connects this space with the interior of the hollow structure I8. A cylindrical member 33 is carried by wall 26 within the hollow structure I8 and extends from the wall to a point beyond the gap 32.

The housing of motor II is formed at the end Y adjacent to the fan with openings 34, while the other end of the housing is formed with openings 35. These openings permit the flow of air within the housing for the purpose'of cooling the motor. A comparatively narrow annular space 36 is provided between the motor suspension ring 25 and the motor housing, whereby some of the air may ow around the outside of the housing. The motor suspension wall 26 is provided with openings 3l which communicate with the channel 38 formed between the hollow structure I8 and the cylindrical member 33.

An end cap 39 is secured to the casing and is provided with an exhaust opening 40, through which the air entering the cap 39 by the openings 3'I may escape to the atmosphere. If it is desired to use the device for blowing purposes, a hose or the like may be connected to the exhaust opening 40.

'Ihe above described device operates as follows:

Upon rotation of the fan by means of motor I1, air is caused to be drawn in through the inlet opening I4 in the cover member II. If a hose and cleaning nozzle is connected to the inlet I4 and the nozzle is passed over a dusty surface, the air will carry with it dust picked I'I from whence it passes through the openings 35 to within the space enclosed by the wall 26 and the cylindrical member 33. The air then passes around the left hand end of the member 33 and thence to the right as viewed in the iigure, through the passage 38 formed between the member 33 and the hollow structure I8. This air passes from this channel through the openings 31 to within the end cap 39 and is nally discharged to the atmosphere through the exhaust opening d0.' A w Sound waves are present in the air owing through channel 38, being caused by the rotation of -the impeller, the rotation of the motor, and the movement of the air through the various passages. The natural resonant frequency of the space M is dependent upon its dimensions and upon the dimensions of the gap 32. If this frequency is the same as the frequency of the sound waves of major intensity in the air passing through the channel 38 it will dampen such sound Waves and greatly reduce their intensity. Of course, the sound waves are not all of the same frequency, but measurements are taken to determine the range of-the frequencies of the sound waves in the air passing through the channel 38, and the space 4I and the gap 32 are then dimensioned so that the natural resonant frequency of the space 4I falls within this range and preferably within the range of the most intense or dominant sound waves, with the result that the sound -waves are dampened and practically eliminated.

Moreover, the ability of the space 4| to dampen sound Waves increases with an increase in its volume, and therefore it is desirable-to have it as large as possible, while maintaining theproper natural resonant frequency by suitably dimensioning the gap 32. As a general rule, the crosssectional area of this gap should be at least as great as the cross-sectional area of the channel 38.

Due to the provision of the annular space 36 between the motor suspension ring 25 and the motor housing. a portion of the air discharged by the fan flows directly therethrough to the channel Sound waves present in the air passing through this space 36 are dampened as the air passes through the channel 38 in the same manner as are the waves present in the air which passes rst through themotor housing and then to the 4channel 38 around the end of cylindrical member Due to the fact that the outer diameter of theY motor housing is less than the outer diameter of the fan impellers. space is provided for the channel 38 without increasing the diameter of the motor-fan unit. Thus, a maximum volume is obtained for the space 4I between'the motor-fan unit and the casing I0.

If desired, the space 4I may be lined with a sound insulating material 42 in order to further reduce the noise emitted by the vacuum cleaner.

While I have illustrated and described one more or less specific embodiment ofmy invention, it is to be understood that this has been done for the purpose of illustration only and that the scope of my invention is not to be limited thereby, but I is to be determined by the appended claims.

What I claim is:

1. In a vacuum cleaner, a casing, hollow structure Within and spaced from said casing to form a space therebetween, a hollow member within and spaced from said hollow structure to form a channel therebetween, an electric motor within said hollow member, and a fan fdriven by said motor for producing flow of air through said channel, said hollow structure being formed with an opening connecting said space with said channel and said space being otherwise closed, said opening and said space being so dimensioned with respect to each other and to said channel that the natural resonant frequency of said space is within'the range of dominant frequencies of the v air flowing through said channel.

38, thus reducing the back pressure of the fan.

2. Ina vacuum cleaner, a casing, hollow cylindrical structure within and spaced from said casing to form a space therebetween, a motor mounted within one end of said structure and spaced from said structure to form a channel therebetween, and a fan impeller mounted on the shaft of said motor within the other end of said structure, said structure serving as a fan housing, said one end of said structure being formed with a passage connecting said channel with said space, said space being otherwise closed, said opening and said space being so dimensioned with respect to each other and to said channel that the natural resonant frequency of said space is within the range of dominant frequencies of the air fiowing through said channel.

ERNST FREDRIK GEORG FREDLUND. 

